Radiant energy is used in a variety of manufacturing processes to treat surfaces, films, and coatings applied to a wide range of materials. Specific processes include but are not limited to curing (i.e., fixing, polymerization), oxidation, purification, and disinfection. Processes using radiant energy to polymerize or effect a desired chemical change is rapid and often less expensive in comparison to a thermal treatment. The radiation can also be localized to control surface processes and allow preferential curing only where the radiation is applied. Curing can also be localized within the coating or thin film to interfacial regions or in the bulk of the coating or thin film. Control of the curing process is achieved through selection of the radiation source type, physical properties (for example, spectral characteristics), spatial and temporal variation of the radiation, and curing chemistry (for example, coating composition).
A variety of radiation sources are used for curing, fixing, polymerization, oxidation, purification, or disinfections due to a variety of applications. Examples of such sources include but are not limited to photon, electron or ion beam sources. Typical photon sources include but are not limited to arc lamps, incandescent lamps, electrodeless lamps and a variety of electronic (i.e., lasers) and solid-state sources.
An apparatus for irradiating a surface with ultraviolet light includes a lamp (e.g., a modular lamp, such as a microwave-powered lamp having a microwave-powered bulb (e.g., tubular bulb) with no electrodes or glass-to-metal seals), the lamp having reflectors to direct light (photons) on to the surface. The source of microwave power is conventionally a magnetron, the same source of microwaves typically found in microwave ovens. The microwave-powered bulb typically receives microwaves generated by the magnetron through an intervening waveguide.
FIG. 1 depicts a conventional assembled magnetron 10 for use in a UV curing lamp assembly, while FIG. 2 depicts an exploded view of the components of the magnetron 10 of FIG. 1. The magnetron 10 comprises a bottom yoke 12 having opposing rails 14 and a plurality of holes 15 formed therein, a bottom magnet 16 overlying the bottom yoke 12, and a cooling assembly 18 overlying the bottom magnet 16 and configured to fit between the opposing rails 14 of the bottom yoke 12. The bottom yoke 12, the bottom magnet 16, and the cooling assembly 18 each have a substantially circular bore hole 20, 22, 24 formed centrally therein and configured for receiving a vacuum tube 26.
Referring now to FIGS. 2 and 3, the vacuum tube 26 has a substantially cylindrical shape and includes a top portion 28 enclosing a filament (not shown) that functions as a cathode, the top portion 28 having a pair of electrical connections 30 extending therefrom and electrically connected to the tube's internal filament (not shown). The top portion 28 overlies a vacuum tube body 32 which functions as an anode. The vacuum tube body 32 overlies an antenna dome 34 extending therefrom, the antenna dome 34 being configured to emit microwave radiation.
Referring again to FIGS. 1 and 2, the vacuum tube 26 is adapted to be inserted in the bore holes 20, 22, 24 such that the antenna dome 34 of the vacuum tube 26 extends a predetermined distance from the bottom yoke 12 and is configured to extend into a cavity of a waveguide (not shown). The bore holes 20, 22 each have substantially the same diameter as the antenna dome 34 of the vacuum tube 26, while the bore hole 24 has substantially the same diameter as the vacuum tube body 32. The small gap between the bore holes 20, 22 and antenna dome 34 contains a metal (stainless steel, brass, etc.) mesh gasket (not shown) to produce a reliable electrical connection with standard waveguide components, thereby reducing rf (radiofrequency) leakage and arcing between the two components. The cooling assembly 18 is typically sized and shaped to fit tightly about the vacuum tube body 32 for the purpose of dissipating heat generated in the vacuum tube 26. In typical configurations, the cooling assembly 18 comprises a plurality of thin plates (“fins”) that are press-fit on to the vacuum tube body (anode) 32 with the assistance of lubricating oil. The top portion 28 of the vacuum tube 26 is configured to receive a top magnet 36 and a top yoke 38 overlying the top magnet 36. The top magnet 36 and the top yoke 38 each have a substantially circular bore hole 40, 42 having substantially the same diameter as the top portion 28 of the vacuum tube 26. A filter/connection box 43 overlies the top yoke 38 and is configured to receive the top portion 28 of the vacuum tube 26 (not shown) to make electrical connection with the filament leads 30. The filter/connection box 43 contains the external connection leads 46, which receive the magnetron input power. The top yoke 38 has a plurality of holes 44 which are adapted to be aligned with corresponding holes 15 in the opposing rails 14 of the bottom yoke 12. The top yoke 38 is fastened to the bottom yoke 12 by means of screws or rivets (not shown) that are inserted into the aligned holes 15, 44 so as to encase the bottom magnet 16, the cooling assembly 18, the vacuum tube 26, and the top magnet 36 therein and forming the assembled magnetron 10.
Many sensitive applications require periodic replacement of magnetrons as a mechanism to ensure optimum process control. In addition, a magnetron may fail and have to be replaced in a UV lamp assembly. The most likely part to fail is the vacuum tube 26, while other parts in the assembled magnetron 10 are much less likely to fail. Moreover, the portions of the assembled magnetron 10 overlying and underlying the vacuum tube 26 carry significant materials (copper, steel, ferrite) that are rarely recycled when a magnetron fails.
Accordingly, what would be desirable, but has not yet been provided, is a magnetron that facilitates replacement of the vacuum tube 26 without having to replace other parts in the magnetron.